Ahmed E. Fazary

Di- and Tri-valent Metal Ions Interactions with Four Biodegradable Hydroxamate and Cataecholate Siderophores: New Insights into Their Complexation Equilibria

The interaction of a number of divalent and trivalent metal ions [iron(III), chromium(III) copper(II), cobalt(II) and nickel(II)] with four isolated and purified microbial catecholate and hydroxamate siderophores was studied using the pH-potentiometric technique to investigate the complexation behavior of these systems as these systems could mimic many biological interactions of the siderophore chelating agent. The protonation constants of these new siderophore analogues as well their binary complex species stability constants were determined using the Hyperquad 2008 estimation model program. From the determined stability constants of the metal complex species, the concentration distribution of the various metal ion complex species involving isolated siderophore analogues in solutions was estimated using the HySS 2009 modeling program. The complex species distribution diagrams were plotted and discussed. Additionally, the Gibbs energies and the molecular structures of the formed complex species were evaluated and predicted using Gaussian 09 software for molecular modeling and density functional theory calculations.

Microbial production of four biodegradable siderophores under submerged fermentation

Four siderophore analogues were isolated and purified from Escherichia coli, Bacillus spp. ST13, and Streptomyces pilosus microorganisms under some specific submerged fermentation conditions. In order to evaluate the highest production of this siderophore analogues through the growth, a rapid spectrophotometric screening semi-quantitative method was used, in which interestingly the analogues were isolated in its own form not its iron chelate. After chromatographic separation, the chemical structures of the isolated and purified siderophores were illustrated using detailed spectroscopic techniques. The biodegradation studies were done on that four novel isolated and purified siderophores following OECD protocols. In addition, the bioactivities of these siderophores and their iron complexes were examined and evaluated.

Synthesis and crystal structures of dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine•dialkylchloroalane(1/1) complexes

Abstract Dialkyl[1,1-bis(alkylchloroalanyl)organylmethyl]phosphine•dialkylchloroalane(1/1) complexes (1a–1d) were synthesized and fully characterized. In 1a–1d, dative bonding between phosphorus or chlorine as a donor atom and aluminum as an acceptor atom results in a bicyclic system. The 31P{1H} NMR spectra of all compounds dissolved in d6-benzene indicate the presence of several isomers in solution. The 27Al{1H} NMR spectra of 1a–1d dissolved in d6-benzene as well show very broad singlets between 177 and 140 ppm. For all compounds, crystal structures consist of two fused four- and five-membered rings. The 1λ3-phosphaalkyne reacts at the Al–C bond of the starting material, whereas the Al–Cl moiety remains intact. The heterocycle isolated is a molecular complex of the underlying insertion compound and a third equivalent of dialkylaluminum chloride. The four- and five-membered rings both contain two chlorine-bridged aluminum atoms, Al3 and Al1, slightly more symmetrical than that between Al1 and Al6. In the four-membered ring the two aluminum atoms Al1 and Al6 approach each other at an average distance of 289.1 pm which tallies with the element–element distance (286.3 pm) in aluminum metal.

Biodegradable siderophores: survey on their production, chelating and complexing properties

Abstract The academic and industrial research on the interactions of complexing agents with the environment has received more attention for more than half a century ago and has always been concerned with the applications of chelating agents in the environment. In contrast, in recent years, an increasing scholarly interest has been demonstrated in the chemical and biological degradation of chelating agents. This is reflected by the increasing number of chelating agents-related publications between 1950 and middle of 2016. Consequently, the discovery of new green biodegradable chelating agents is of great importance and has an impact in the non-biodegradable chelating agent’s replacement with their green chemistry analogs. To acquire iron, many bacteria growing aerobically, including marine species, produce siderophores, which are low-molecular-weight compounds produced to facilitate acquisition of iron. To date and to the best of our knowledge, this is a concise and complete review article of the current and previous relevant studies conducted in the field of production, purification of siderophore compounds and their metal complexes, and their roles in biology and medicine.

Bioactivities of Novel Metal Complexes Involving B Vitamins and Glycine

Abstract In this work twelve novel mixed ligand complexes were synthesized. The complexes were formed between a metal ion (Cu(II), Cd(II), Mn(II), Fe(III), Ni(II), Pb(II)) and vitamins (B 3 and B 9) as primary ligands, and glycine as secondary ligand. Melting points, conductivities, and magnetic susceptibilities of the synthesized complexes were determined and the complexes were subjected to elemental analyses. The presence of coordination water molecules in the complex was also supported by TG/DTG thermal analysis. Full elucidation of the molecular structures for the synthesized mixed ligand complexes were confirmed using detailed spectroscopic IR, 1H-, 13C-NMR, and XRD techniques. In addition, cytotoxic and antioxidant activities of the twelve synthesized solid complexes were tested to evaluate their bioactivities.

Platinum and vanadate Bioactive Complexes of Glycoside Naringin and Phenolates

Abstract Platinum(II) and vanadium(V) solid binary and ternary complexes involving naringin, a flavanone glycoside in found in grapefruit, and some phenolic acids were synthesized and fully characterized using detailed structural and spectroscopic analysis techniques such as IR, NMR, and SEM techniques. The magnetic susceptibility results as well line drawings of the platinum and vanadium complexes showed four-coordinate square-planar and remarkable low-spin diamagnetic species; which is in agreement with the structures proposed. The cytotoxic activities of the binary and ternary vanadium and platinum metal complexes of phenolic acids and naringin were tested and evaluated against HepG2 (human hepatocellular carcinoma), MCF-7 (human breast adenocarcinoma), and HCT116 (human colorectal carcinoma) tumor cell lines. Also, their antioxidant activities were examined by free radical scavenging assay. The relationship between the chemical structure of the synthesized complexes and their biological influence was studied and evaluated.

Norleucine metal complexes: comments on their equilibrium constants data

Abstract This discussion article summarizes all protonation and stability constants data found in the literature for nonprotein l-norleucine amino acid and its metal complexes. The results of approximately 18 published articles discussing the protonation and complexation equilibria of l-norleucine using different techniques and software were presented to comprehend the data on the grounds of modern aspects of l-norleucine complex chemistry.

Commentary on the Synthesis and Structures of Unsupported Cycloarsoxane Compounds

This comment describes the available synthetic routes and some general structural features of unsupported cycloarsoxane compounds. The key synthetic strategies used to prepare this type of compound and the significant roles that they have been employed in after coordination to the metal center are fully discussed. The literature herein covers all known unsupported cycloarsoxane compounds that have been structurally characterized by X-ray diffraction techniques.

Bioactive Lignans: A Survey Report on their Chemical Structures?

Lignans are polyphenols spread in a wide variety of plant-based foods, including seeds, whole grains, legumes, fruit, and vegetables. When consumed, lignan precursors are converted to the enterolignans, enterodiol and enterolactone, by bacteria that normally colonize the human intestine. Lignans have attracted considerable attention due to their pharmacological and biological activities. This review article is a survey on the molecular structure of about 276 new naturally occurring lignans obtained from different plant families. We classified seven main types according to their structural features, and provided a number of review reports published recently about lignans. A tabular compilation of the molecular structures of known lignans is presented at the end of this survey report. A total of 111 references were considered for this survey report.